Techniques for direct secondary cell activation using temporary reference signals

1 . A method for wireless communication at a user equipment (UE), comprising:

receiving, via a first serving cell, a radio resource control message comprising an indication to activate a second serving cell different from the first serving cell;

transmitting, via the first serving cell in response to the radio resource control message, a radio resource control response message acknowledging the radio resource control message;

identifying, within an activation time interval following transmission of the radio resource control response message and based at least in part on the radio resource control message, a resource for a reference signal associated with time and frequency tracking for the second serving cell; and

monitoring the resource for the reference signal based at least in part on the identifying.

2 . The method of claim 1 , further comprising:

receiving, via the radio resource control message, an indication of the resource for the reference signal, wherein identifying the resource, monitoring the resource, or both, is based at least in part on receiving the radio resource control message.

3 . The method of claim 1 , further comprising:

receiving, via the first serving cell based at least in part on receiving the radio resource control message, a control message comprising an indication of the resource for the reference signal, wherein identifying the resource, monitoring the resource, or both, is based at least in part on receiving the control message.

4 . The method of claim 3 , wherein the control message comprises a medium access control-control element message that is received via the first serving cell after reception of the radio resource control message.

5 . The method of claim 3 , wherein the control message comprises a downlink control information message that is received via the first serving cell within the activation time interval.

6 . The method of claim 1 , further comprising:

receiving the radio resource control message, additional control signaling, or both, indicating one or more parameters associated with the reference signal, wherein monitoring the resource is based at least in part on the one or more parameters.

7 . The method of claim 6 , wherein the one or more parameters comprise a structure of the reference signal, a component carrier for the reference signal, a bandwidth part for the reference signal, or any combination thereof.

8 . The method of claim 1 , further comprising:

receiving the radio resource control message, additional control signaling, or both, indicating one or more active transmission configuration indicator states associated with the second serving cell, wherein the resource for the reference signal is monitored based at least in part on an active transmission configuration indicator state of the one or more active transmission configuration indicator states.

9 . The method of claim 1 , further comprising:

receiving the reference signal via the second serving cell based at least in part on the monitoring; and

communicating with the second serving cell based at least in part on time and frequency tracking information determined using the reference signal.

10 . The method of claim 9 , further comprising:

receiving, via the reference signal, automatic gain control information associated with the second serving cell, wherein communicating with the second serving cell is based at least in part on the automatic gain control information.

11 . The method of claim 9 , wherein the reference signal is received prior to an earliest synchronization signal block which the UE is capable of receiving via the second serving cell.

12 . The method of claim 1 , wherein the reference signal comprises a temporary reference signal, a tracking reference signal, a non-zero power channel state information reference signal, or any combination thereof.

13 . A method for wireless communication at a base station, comprising:

transmitting, to a user equipment (UE) via a first serving cell supported by the base station, a radio resource control message comprising an indication for the UE to activate a second serving cell supported by the base station which is different from the first serving cell;

receiving, from the UE via the first serving cell in response to the radio resource control message, a radio resource control response message acknowledging the radio resource control message; and

transmitting, to the UE via the second serving cell within an activation time interval following reception of the radio resource control response message and based at least in part on the radio resource control message, a reference signal associated with time and frequency tracking for the second serving cell.

14 . The method of claim 13 , further comprising:

transmitting, via the radio resource control message, an indication of a resource for the reference signal, wherein transmitting the reference signal is based at least in part on transmitting the radio resource control message.

15 . The method of claim 13 , further comprising:

transmitting, via the first serving cell based at least in part on transmitting the radio resource control message, a control message comprising an indication of a resource for the reference signal, wherein transmitting the reference signal is based at least in part on transmitting the control message.

16 . The method of claim 15 , wherein the control message comprises a medium access control-control element message that is transmitted via the first serving cell after transmission of the radio resource control message.

17 . The method of claim 15 , wherein the control message comprises a downlink control information message that is transmitted via the first serving cell within the activation time interval.

18 . The method of claim 13 , further comprising:

transmitting the radio resource control message, additional control signaling, or both, indicating one or more parameters associated with the reference signal, wherein transmitting the reference signal is based at least in part on the one or more parameters.

19 . The method of claim 18 , wherein the one or more parameters comprise a structure of the reference signal, a component carrier for the reference signal, a bandwidth part for the reference signal, or any combination thereof.

20 . The method of claim 13 , further comprising:

transmitting the radio resource control message, additional control signaling, or both, indicating one or more active transmission configuration indicator states associated with the second serving cell, wherein the reference signal is transmitted in accordance with an active transmission configuration indicator state of the one or more active transmission configuration indicator states.

21 . The method of claim 13 , further comprising:

communicating with the UE via the second serving cell based at least in part on transmitting the reference signal.

22 . The method of claim 21 , further comprising:

transmitting, via the reference signal, automatic gain control information associated with the second serving cell, wherein communicating with the second serving cell is based at least in part on the automatic gain control information.

23 . The method of claim 21 , wherein the reference signal is transmitted prior to an earliest synchronization signal block which the UE is capable of receiving via the second serving cell.

24 . The method of claim 13 , wherein the reference signal comprises a temporary reference signal, a tracking reference signal, a non-zero power channel state information reference signal, or any combination thereof.

25 . A user equipment (UE), comprising:

one or more processors;

one or more memories coupled with the one or more processors; and

instructions stored in the one or more memories and executable by the one or more processors to cause the UE to:

receive, via a first serving cell, a radio resource control message comprising an indication to activate a second serving cell different from the first serving cell;

transmit, via the first serving cell in response to the radio resource control message, a radio resource control response message acknowledging the radio resource control message;

identify, within an activation time interval following transmission of the radio resource control response message and based at least in part on the radio resource control message, a resource for a reference signal associated with time and frequency tracking for the second serving cell; and

monitor the resource for the reference signal based at least in part on the identifying.

26 . The UE of claim 25 , wherein the instructions are further executable by the one or more processors to cause the UE to:

receive, via the radio resource control message, an indication of the resource for the reference signal, wherein identifying the resource, monitoring the resource, or both, is based at least in part on receiving the radio resource control message.

27 . The UE of claim 25 , wherein the instructions are further executable by the one or more processors to cause the UE to:

receive, via the first serving cell based at least in part on receiving the radio resource control message, a control message comprising an indication of the resource for the reference signal, wherein identifying the resource, monitoring the resource, or both, is based at least in part on receiving the control message.

28 . A base station, comprising:

one or more processors;

one or more memories coupled with the one or more processors; and

instructions stored in the one or more memories and executable by the one or more processors to cause the base station to:

transmit, to a user equipment (UE) via a first serving cell supported by the base station, a radio resource control message comprising an indication for the UE to activate a second serving cell supported by the base station which is different from the first serving cell;

receive, from the UE via the first serving cell in response to the radio resource control message, a radio resource control response message acknowledging the radio resource control message; and

transmit, to the UE via the second serving cell within an activation time interval following reception of the radio resource control response message and based at least in part on the radio resource control message, a reference signal associated with time and frequency tracking for the second serving cell.

29 . The base station of claim 28 , wherein the instructions are further executable by the one or more processors to cause the base station to:

transmit, via the radio resource control message, an indication of a resource for the reference signal, wherein transmitting the reference signal is based at least in part on transmitting the radio resource control message.

30 . The base station of claim 28 , wherein the instructions are further executable by the one or more processors to cause the base station to:

transmit, via the first serving cell based at least in part on transmitting the radio resource control message, a control message comprising an indication of a resource for the reference signal, wherein transmitting the reference signal is based at least in part on transmitting the control message.